1. Field of the Invention
The present invention relates to a data communication system and method for communicating processed data between processor elements coupled with each other via a data communication network. More particularly, this invention is concerned with a data communication system and method that guarantees the communication of processed data between processor elements constituting a parallel-processing machine.
2. Description of the Related Art
In the field of computers, the adoption of parallel processing aims at a remarkable improvement in throughput. In a computer operating as this kind of parallel-processing machine, a plurality of processing elements are coupled with one another via a data communication network such as a crossbar network including communication buffers. Unprocessed and processed data are transferred between processor elements. At this time, synchronous control is carried out to confirm the termination of data transfer between the processor elements and to proceed to the next parallel processing. The synchronous control makes it necessary to confirm that transfer data has reached a receiving station. It is therefor a must for improvement of the performance of a parallel-processing machine to guarantee the data communication with a simple hardware configuration at a high speed.
In a data communication system for transferring data via a data communication network such as a crossbar network including multiple buffers, the communication buffer length or a maximum communication buffer length for transmitting data from a transmitter to a receiver has been determined on a fixed basis, but the transfer time has not always been fixed. The reason why the transfer time is not determined on a fixed basis is that even when a receiver is coupled with a transmitter via a data communication network, if the receiver is busy, it cannot receive data. When a data communication network is a network made up of crossbar switches, if multiple transmitters send data to the same receiver, data from specific transmitters approach the receiver in the specified order of priorities. At some time instant, data transfer proceeds only for the data from one transmitter according to a defined order of priorities, and the other transmitters are forced to wait for the completion of the data transfer. As mentioned above, when a communication buffer length is fixed but a transfer time is not fixed, it must be guaranteed that data from a transmitter has reached a receiver. In a conventional method for providing this guarantee, the receiver uses a leased line to return a reception end signal to the transmitter or the receiver uses a data communication network to return a reception end signal to the transmitter.
However, in the method that a receiver uses a leased control line to return a reception end signal to a transmitter, additional hardware is required to return a reception end signal. In the method that a receiver uses a data communication network to return a reception end signal. returnable data that represents termination of reception must be created at a receiving end. When hardware is used to create the returnable data, circuits become complex and large in scale. When software is used to create the returnable data, a prolonged period of processing time becomes necessary. In either of the methods, a time lag occurs after a receiver completes data reception until a transmitter is informed of termination of reception. This restricts the performance of a parallel-processing machine having numerous processor elements.